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  • Stainless to Copper Welding Cracking Help

    I've done a little Stainless to Copper Welding and it's hard but I've got it to work. I've just done some more and one area was fine but then when welding the ends of the tubing I was joining it got some stress cracks after I removed the heat. I'm sure its just because of the two dissimilar metals cooling at different rates that does this, but how do I over come this?

    I'm using regular Tig with Argon set at 15 and 316 Stainless 1/8" filler rod 1/2" Cup and a 3/32 Ceriated Tungsten. I tried preheating with propane torch and heating after, but it seems to crack instantly.

    Here are some pics. Basically I welded a sch.10 stainless pipe into a 4" Tri Clover Cap then slipped the 2" copper plumbing tube inside that and welded it. Where the tube enters the pipe came out fine, but when I turned it over and welding the end of the copper tube to the end of the stainless pipe, that's where it cracked. I kept adding more filler metal to see if it would stop cracking but it didn't help. The end pic is hard to see but you can see the cracks.

    Any suggestions would be helpful. Thanks.

    Click image for larger version

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  • #2
    I dont have any experience with this, but i think you are using the wrong filler.

    I googled around a bit at it looks like you want to use ERCuAl-A2.

    or maybe try hastelloy W.

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    • #3
      Silicone bronze should be a player also.

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      • #4
        On the end that cracked were you bridging a gap or was it a tight fit? If you're bridging a gap I would have drilled a small hole in the stainless tube and purged so that the back side wouldn't sugar when adding the stainless rod.

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        • #5
          #1. You need to do a lot more study on "welding dissimilar metals".

          #2. SS to copper is a real challenge because of the thermal conductivity of the two base material. (SS very low. Copper very high)

          #3. Do a google search on "welding stainless steel to copper". You'll find that the "recommended filler is ERCuAl-A2 or ERCu-Ni3".

          #4. Not trying to be an Azz, but I don't see a "weld bead" in the photo you posted. Looks more like seagull droppings. I see a lot more "hood time" needed before you even hope to be successful in this attemped weld. What I see in your photo is a lot of filler melted on your base material.

          #5. You may be more successful with a silver solder than you are trying to tig weld it.
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          • #6
            Dont weld it. Silver Braze it.

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            • #7
              I've done research in the past on this and because it's has to be food grade I was told to use SS316.

              Thanks for the help. A little late to braze.

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              • #8
                Food grade?

                Do you know what "food grade" means?

                Purge?

                If the specs call for "food grade", you really should really take this part to someone that knows what they're doing. What you've got there is nowhere close.
                Last edited by SundownIII; 09-29-2010, 06:01 PM.
                Syncrowave 250 DX Tigrunner
                Dynasty 200 DX
                Miller XMT 304 w/714D Feeder & Optima Control
                Miller MM 251 w/Q300 & 30A SG
                Hobart HH187
                Dialarc 250 AC/DC
                Hypertherm PM 600 & 1250
                Wilton 7"x12" bandsaw
                PC Dry Cut Saw, Dewalt Chop Saw
                Milwaukee 8" Metal Cut Saw, Milwaukee Portaband.
                Thermco and Smith (2) Gas Mixers
                More grinders than hands

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                • #9
                  Originally posted by SundownIII View Post
                  If the specs call for "food grade", you really should really take this part to someone that knows what they're doing. What you've got there is nowhere close.
                  yeah, there is no way id eat that thing.

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                  • #10
                    This must be a joke

                    You can't be serious.

                    Food Grade Sanitary Weld

                    You must be either joking or have no clue (possibly both)

                    Not even close with the required filler type, and you don't have the skill even if you did get the right filler

                    Enjoy building your moonshine still cause that's probably what you are trying to make (I'll pass on having any of that brew)
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                    • #11
                      I have never welded copper to stainless in a food grade situation, you could try a clamp fitting similar to what you have with one half machined from copper or a screwed fitting, pipe thread or similar to do it but then it isnt food grade anymore. I have used fittings like this for water connections but they are not food grade.
                      mike sr

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                      • #12
                        Ok, I have to chime in.

                        "Food Grade" basically means constructed so that the final product will not allow cracks or mismatches or discontinuities that may trap debris or foreign matter that can contaminate the food product.

                        Since you have been directed to arc weld copper to stainless, really you should have used silicon bronze, getting full penetration, or welding from both sides, and blending or smoothing the weld if it may trap food that can rot or harbor bacteria, and any disinfectant that runs the circuit between batches.

                        Most food grade on SS pipe and tube in my shop has been done full pen, with a purge, and inspected for smooth joints. In a lot of cases flourescent pen inspect is required.

                        I agree that 316L would be the preferred choice but only for SS to SS. My experience comes primarily from doing work for the frozen food manufactures and brewing industry here in Los Angeles.
                        Nothing welded, Nothing gained

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                        • #13
                          yep, looks like the lid and column for a reflux still. Get a stainless threaded end for the lid and copper threaded end for the column. The lid might warp, might have to rig some edges to hold it down with small C clamps. Use a seal made with a flour and water doe. Roll it out like a rope and place around the top after you put in the wash.

                          Makes a great seal, especially if your heating with an open flame.

                          Or maybe it's not a still.

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                          • #14
                            I thought the same about it being part of a still. Here is a sample of copper welded to stainless, I used 316 filler wire and purged the inside. With a tight fit it welded fine and the drop thru was clean. I wouldn't use it for pressure piping but for it's purpose it works well.
                            Regards
                            Jim
                            Attached Files

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                            • #15
                              Looks nice Jim, lets see the whole thing.

                              Is that a Keg?

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